1. Field of the Invention
The invention relates to biodegradable oligoesters suitable as lubricants, made from a tricyclic diol with 8 to 20 carbon atoms, a saturated, straight-chain or branched dicarboxylic acid with 4 to 20 carbon atoms, and an aliphatic alcohol with 1 to 30 carbon atoms, as well as the use of these oligoesters as lubricants. The oligoesters according to the invention have a kinematic viscosity of 50 to 50,000 mm.sup.2 /s at 40.degree. C.
2. Discussion of the Background
Synthetic esters, such as aliphatic and aromatic dicarboxylic acid diesters, dimeric acid esters and pentaerythritol tetraesters, for example, as well as natural esters such as canola oil, are used in lubricant technology in many different areas. They are characterized by good lubricant properties and have a high viscosity index, unless they are aromatic esters, and are generally easily biodegradable, in contrast to products based on mineral oil and other hydrocarbons, such as poly(alpha-olefins).
Until now, ester oils with high viscosity that have a low solidification point, are biodegradable and demonstrate good lubricant properties have not been available. The canola oils and dimeric acid esters which have a relatively high viscosity tend to gum up, because of the double bond which is still present, and are very sensitive to oxidation, so that there are many purposes for which they cannot be used.